Quantum anti-Zeno effect in artificial quantum systems

In this paper, we study a quantum anti-Zeno effect (QAZE) purely induced by repetitive measurements for an artificial atom interacting with a structured bath. This bath can be artificially realized with coupled resonators in one dimension and possesses photonic band structure like Bloch electron in a periodic potential. In the presence of repetitive measurements, the pure QAZE is discovered as the observable decay is not negligible even for the atomic energy level spacing outside of the energy band of the artificial bath. If there were no measurements, the decay would not happen outside of the band. In this sense, the enhanced decay is completely induced by measurements through the relaxation channels provided by the bath. Besides, we also discuss the controversial golden rule decay rates originated from the van Hove's singularities and the effects of the counter-rotating terms.Comment: 12 pages, 8 figure

Charge Qubit Storage and Its Engineered Decoherence via Microwave Cavity

We study the entanglement of the superconducting charge qubit with the quantized electromagnetic field in a microwave cavity. It can be controlled dynamically by a classical external field threading the SQUID within the charge qubit. Utilizing the controllable quantum entanglement, we can demonstrate the dynamic process of the quantum storage of information carried by charge qubit. On the other hand, based on this engineered quantum entanglement, we can also demonstrate a progressive decoherence of charge qubit with quantum jump due to the coupling with the cavity field in quasi-classical state.Comment: 6 pages, 4 figure

A tunable radiation source by coupling laser-plasma-generated electrons to a periodic structure

Near-infrared radiation around 1000 nm generated from the interaction of a high-density MeV electron beam, obtained by impinging an intense ultrashort laser pulse on a solid target, with a metal grating is observed experimentally. Theoretical modeling and particle-in-cell simulation suggest that the radiation is caused by the Smith-Purcell mechanism. The results here indicate that tunable terahertz radiation with tens GV=m field strength can be achieved by using appropriate grating parameter

Interactions between energetic electrons and realistic whistler mode waves in the Jovian magnetosphere

The role of plasma waves in shaping the intense Jovian radiation belts is not well understood. In this study we use a realistic wave model based on an extensive survey from the Plasma Wave Investigation on the Galileo spacecraft to calculate the effect of pitch angle and energy diffusion on Jovian energetic electrons due to upper and lower band chorus. Two Earth-based models, the Full Diffusion Code and the Versatile Electron Radiation Belt code, are adapted to the case of the Jovian magnetosphere and used to resolve the interaction between chorus and electrons at L = 10. We also present a study of the sensitivity to the latitudinal wave coverage and initial electron distribution. Our analysis shows that the contribution to the electron dynamics from upper band chorus is almost negligible compared to that from lower band chorus. For 100 keV electrons, we observe that diffusion leads to redistribution of particles toward lower pitch angles with some particle loss, which could indicate that radial diffusion or interchange instabilities are important. For energies above >500 keV, an initial electron distribution based on observations is only weakly affected by chorus waves. Ideally, we would require the initial electron phase space density before transport takes place to assess the importance of wave acceleration, but this is not available. It is clear from this study that the shape of the electron phase space density and the latitudinal extent of the waves are important for both electron acceleration and loss

In-plane magnetic reorientation in coupled ferro- and antiferromagnetic thin films

By studying coupled ferro- (FM) and antiferromagnetic (AFM) thin film systems, we obtain an in-plane magnetic reorientation as a function of temperature and FM film thickness. The interlayer exchange coupling causes a uniaxial anisotropy, which may compete with the intrinsic anisotropy of the FM film. Depending on the latter the total in-plane anisotropy of the FM film is either enhanced or reduced. Eventually a change of sign occurs, resulting in an in-plane magnetic reorientation between a collinear and an orthogonal magnetic arrangement of the two subsystems. A canted magnetic arrangement may occur, mediating between these two extremes. By measuring the anisotropy below and above the N\'eel temperature the interlayer exchange coupling can be determined. The calculations have been performed with a Heisenberg-like Hamiltonian by application of a two-spin mean-field theory.Comment: 4 pages, 4 figure

Correlation effects and the high-frequency spin susceptibility of an electron liquid: Exact limits

Spin correlations in an interacting electron liquid are studied in the high-frequency limit and in both two and three dimensions. The third-moment sum rule is evaluated and used to derive exact limiting forms (at both long- and short-wavelengths) for the spin-antisymmetric local-field factor, $\lim_{\omega \to \infty}G_-({\bf q, \omega})$. In two dimensions $\lim_{\omega \to \infty}G_-({\bf q, \omega})$ is found to diverge as $1/q$ at long wavelengths, and the spin-antisymmetric exchange-correlation kernel of time-dependent spin density functional theory diverges as $1/q^2$ in both two and three dimensions. These signal a failure of the local-density approximation, one that can be redressed by alternative approaches.Comment: 5 page

Effect of tea soil acidification on the diversity and function of fungi community

Soil fungi play an important role in the process of planting tea tree. However, effects of acidification on the diversity and function of the fungi community in tea rhizosphere soil have been rarely reported. In this study, tea rhizosphere soils with pH of 3.3, 4.7, 5.3 and 6.4 were investigated for diversity and function of fungal communities through T-RFLP technology. The results showed that the abundance and diversity of fungi increased significantly with the decrease of pH value of rhizosphere soil. The results of significance analysis showed that 38 T-RFs fragments were significantly correlated with pH value, among which 32 were negatively correlated with pH value and 6 were positively correlated with pH value. After database comparison, 23 fungi were identified and classified according to their nutritional patterns, which can be divided into four types, including pathotroph, symbiotroph, saprotroph and unknown, accounting for 36.85%, 7.89%, 15.79% and 39.47%, respectively. At pH value of 3.3, the fungus abundance reached the maximum value. In conclusion, acidification leads to changes in the structure and diversity of the fungi community in tea rhizosphere soil, specifically, a significant increase in the number and species of fungi, of which the pathotroph type is the largest. This study provides an important theoretical basis for controlling fungal diseases of tea tree in acidified tea plantation

A study of the optical and radiation damage properties of lead tungstate crystals

Lead tungstate (PbWO{sub 4}) is a new scintillating material which is of great interest for use in high energy electromagnetic calorimeters. It has a very high density, short radiation length and small Moliere radius and has a scintillation light output which peaks between 450--550 nm with a decay time in the range from 5--15 ns. It is presently being considered for use in two large, high resolution electromagnetic calorimeters, one for the CMS experiment and the other for the ALICE experiment, at the Large Hadron Collider at CERN. In order to meet the stringent demands of these two experiments, the crystals are required to be of high purity, produced uniform light output, and, in the case of CMS, be resistant to radiation damage up to several megarads. Here, a study has been made of the optical and radiation damage properties of undoped and niobium doped lead tungstate crystals. Data were obtained on the optical absorbance, the intensity and decay time of the scintillation light output, and the radioluminescence and photoluminescence emission spectra. Radiation damage was studied in several undoped and niobium doped samples using {sup 60}Co gamma ray irradiation. The change in optical absorption and observed scintillation light output was measured as a function of dose up to total cumulative doses on the order of 800 krad. The radiation induced phosphorescence and thermoluminescence was also measured, as well as recovery from damage by optical bleaching and thermal annealing. An investigation was also made to determine trace element impurities in several samples

Measurement of the Intrinsic Radiopurity of Cs-137/U-235/U-238/Th-232 in CsI(Tl) Crystal Scintillators

The inorganic crystal scintillator CsI(Tl) has been used for low energy neutrino and Dark Matter experiments, where the intrinsic radiopurity is an issue of major importance. Low-background data were taken with a CsI(Tl) crystal array at the Kuo-Sheng Reactor Neutrino Laboratory. The pulse shape discrimination capabilities of the crystal, as well as the temporal and spatial correlations of the events, provide powerful means of measuring the intrinsic radiopurity of Cs-137 as well as the U-235, U-238 and Th-232 series. The event selection algorithms are described, with which the decay half-lives of Po-218, Po-214, Rn-220, Po-216 and Po-212 were derived. The measurements of the contamination levels, their concentration gradients with the crystal growth axis, and the uniformity among different crystal samples, are reported. The radiopurity in the U-238 and Th-232 series are comparable to those of the best reported in other crystal scintillators. Significant improvements in measurement sensitivities were achieved, similar to those from dedicated massive liquid scintillator detector. This analysis also provides in situ measurements of the detector performance parameters, such as spatial resolution, quenching factors, and data acquisition dead time.Comment: 28 pages, 12 figure

Measurements of the observed cross sections for e+e−→e^+e^-\to exclusive light hadrons containing π0π0\pi^0\pi^0 at s=3.773\sqrt s= 3.773, 3.650 and 3.6648 GeV

By analyzing the data sets of 17.3, 6.5 and 1.0 pb$^{-1}$ taken, respectively, at $\sqrt s= 3.773$, 3.650 and 3.6648 GeV with the BES-II detector at the BEPC collider, we measure the observed cross sections for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$, $K^+K^-\pi^0\pi^0$, $2(\pi^+\pi^-\pi^0)$, $K^+K^-\pi^+\pi^-\pi^0\pi^0$ and $3(\pi^+\pi^-)\pi^0\pi^0$ at the three energy points. Based on these cross sections we set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay into these final states at 90% C.L..Comment: 7 pages, 2 figure